[PATCH] mm: ptd_alloc take ptlock
Second step in pushing down the page_table_lock. Remove the temporary
bridging hack from __pud_alloc, __pmd_alloc, __pte_alloc: expect callers not
to hold page_table_lock, whether it's on init_mm or a user mm; take
page_table_lock internally to check if a racing task already allocated.
Convert their callers from common code. But avoid coming back to change them
again later: instead of moving the spin_lock(&mm->page_table_lock) down,
switch over to new macros pte_alloc_map_lock and pte_unmap_unlock, which
encapsulate the mapping+locking and unlocking+unmapping together, and in the
end may use alternatives to the mm page_table_lock itself.
These callers all hold mmap_sem (some exclusively, some not), so at no level
can a page table be whipped away from beneath them; and pte_alloc uses the
"atomic" pmd_present to test whether it needs to allocate. It appears that on
all arches we can safely descend without page_table_lock.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/mm/fremap.c b/mm/fremap.c
index 49719a3..d862be3 100644
--- a/mm/fremap.c
+++ b/mm/fremap.c
@@ -63,23 +63,20 @@
pud_t *pud;
pgd_t *pgd;
pte_t pte_val;
+ spinlock_t *ptl;
BUG_ON(vma->vm_flags & VM_RESERVED);
pgd = pgd_offset(mm, addr);
- spin_lock(&mm->page_table_lock);
-
pud = pud_alloc(mm, pgd, addr);
if (!pud)
- goto err_unlock;
-
+ goto out;
pmd = pmd_alloc(mm, pud, addr);
if (!pmd)
- goto err_unlock;
-
- pte = pte_alloc_map(mm, pmd, addr);
+ goto out;
+ pte = pte_alloc_map_lock(mm, pmd, addr, &ptl);
if (!pte)
- goto err_unlock;
+ goto out;
/*
* This page may have been truncated. Tell the
@@ -89,10 +86,10 @@
inode = vma->vm_file->f_mapping->host;
size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
if (!page->mapping || page->index >= size)
- goto err_unlock;
+ goto unlock;
err = -ENOMEM;
if (page_mapcount(page) > INT_MAX/2)
- goto err_unlock;
+ goto unlock;
if (pte_none(*pte) || !zap_pte(mm, vma, addr, pte))
inc_mm_counter(mm, file_rss);
@@ -101,17 +98,15 @@
set_pte_at(mm, addr, pte, mk_pte(page, prot));
page_add_file_rmap(page);
pte_val = *pte;
- pte_unmap(pte);
update_mmu_cache(vma, addr, pte_val);
-
err = 0;
-err_unlock:
- spin_unlock(&mm->page_table_lock);
+unlock:
+ pte_unmap_unlock(pte, ptl);
+out:
return err;
}
EXPORT_SYMBOL(install_page);
-
/*
* Install a file pte to a given virtual memory address, release any
* previously existing mapping.
@@ -125,23 +120,20 @@
pud_t *pud;
pgd_t *pgd;
pte_t pte_val;
+ spinlock_t *ptl;
BUG_ON(vma->vm_flags & VM_RESERVED);
pgd = pgd_offset(mm, addr);
- spin_lock(&mm->page_table_lock);
-
pud = pud_alloc(mm, pgd, addr);
if (!pud)
- goto err_unlock;
-
+ goto out;
pmd = pmd_alloc(mm, pud, addr);
if (!pmd)
- goto err_unlock;
-
- pte = pte_alloc_map(mm, pmd, addr);
+ goto out;
+ pte = pte_alloc_map_lock(mm, pmd, addr, &ptl);
if (!pte)
- goto err_unlock;
+ goto out;
if (!pte_none(*pte) && zap_pte(mm, vma, addr, pte)) {
update_hiwater_rss(mm);
@@ -150,17 +142,13 @@
set_pte_at(mm, addr, pte, pgoff_to_pte(pgoff));
pte_val = *pte;
- pte_unmap(pte);
update_mmu_cache(vma, addr, pte_val);
- spin_unlock(&mm->page_table_lock);
- return 0;
-
-err_unlock:
- spin_unlock(&mm->page_table_lock);
+ pte_unmap_unlock(pte, ptl);
+ err = 0;
+out:
return err;
}
-
/***
* sys_remap_file_pages - remap arbitrary pages of a shared backing store
* file within an existing vma.